Blood oxygenators are well known and are routinely used to temporarily assume the function of the lungs in certain surgical procedures such as open heart surgery. Although the principal function of the oxygenator is to store blood and conduct an oxygen-carbon dioxide gas exchange with the patient's blood, it also traditionally serves the function of regulating the blood temperature as various phases of the surgery require.
In a conventional oxygenator, blood temperature is regulated by causing the blood to flow through a heat exchanger in which a heat exchange takes place through metal or plastic interfaces between the blood and a temperature-controlled stream of water. The heat exchanger is conventionally incorporated into the oxygenator so that the blood follows a continuous path in the oxygenator, first through the heat exchanger and then through the gas exchanger.
Whenever blood and water are present in the same device, there is an inherent danger that one may accidentally leak into the other and interfere with the patient's well-being. Also, the water connection lines to the oxygenator, which is usually mounted on the heart-lung machine, can become snagged and lead to accidents. Equipment is further required for controlling the water temperature.
Placing the temperature control equipment directly into the oxygenator would solve the water problem, but this is impractical because the required equipment would be too bulky to fit into a reasonably sized oxygenator, and because the equipment would be too expensive for incorporation in a disposable device, which the oxygenator must be.